PSI - Issue 19

Shinji Hashimura et al. / Procedia Structural Integrity 19 (2019) 204–213 Author name / Structural Integrity Procedia 00 (2019) 000–000

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3

Fig. 1 Haigh diagram of high strength steel bolts which was proposed by Yoshimoto et al. (1983).

(

)       ) 0 0 2





0 w T

T w . 



(1)

w

(

K



f

where  w is the fatigue limit of bolt,  w 0 is the fatigue strength of a smooth specimen of the bolt material.  T is the true ultimate strength and  0.2 is the proof stress of the bolt material. K f is the fatigue notch factor at the root of the first thread of bolt.

Nomenclature

Fatigue strength of the smooth specimen

 w 0

Fatigue strength of the bolt Proof stress of the bolt material

 w

 0.2

True ultimate strength

 T  m

Mean stress

Stress amplitude Maximum stress Minimum stress

 a

 max  min

Fatigue notch factor Nominal length of bolt Nominal length of bolt

K f

l

l g

Mean load

Q m

Load amplitude Clamp force

 Q a

F

Number of cycles to failure

N f

3. Fatigue tests Figure 2 shows the schematic illustrations of test bolt and test nut. The test bolts were a commercial full threaded hexagon head bolt M8 made of aluminum alloy A5056 and A6056-T6. The thread pitch was course pitch 1.25 mm. The nominal length was l =40 mm. The test nut was a commercial hexagon nut. The test nut for A5056 bolt was a commercial hexagon nuts made of aluminum alloy A5056. The test nut for A6056 bolt was made of the aluminum alloy die castings material Al-12Si-Cu alloy (ADC12) taking the actual usage into account. The ADC12 nuts were